Cold Perception

A person's perception of warm and cold on a bicycle has always been something that has interested me. On any given day, one person may feel ok riding in shorts with no beanie, while another person will feel the need to wear long underwear, gloves, stocking cap, and winter jacket. Also, the same person may feel the need to wear more clothing on Monday than on Friday, even though the temperatures were identical on those days. Is it all psychological? Do we just wake up some mornings feeling colder than other mornings?
I myself always lean towards wearing more clothes than less (unless it's a naked ride), because it's much easier to cool off than it is to warm up. These two pictures were both taken today, about 2 minutes apart, the above commuter obviously felt like it was a warm day while the below commuter was more like me, feeling that more clothes are better.